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ANATOMY OF THE GALL BLADDER

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Different Pattern Of Presentation Of Carcinoma Gallbladder And Management. INTRODUCTION

Carcinoma of the gallbladder (CaGB) is the most common malignant lesion of the biliary tract and holds fifth place among all malignant neoplasms of the digestive tract. It (CaGB) is a highly lethal disease. In over 70-80% cases, it is associated with cholelithiasis, although a correlation between these two cannot be determined with certainty.1 Even today, with multiple diagnostic tests available, gallbladder cancer is usually first recognized during a laparotomy performed for presumptive diagnosis of benign gallbladder disease. One to two percent patients undergoing operations for cholelithiasis have the diagnosis made incidentally at the time of surgical exploration.2 In India, however, the majority are discovered with advanced disease during ultrasonography for upper abdominal symptoms. In our country, the picture is almost same.

The incidence of gallbladder cancer varies greatly in different areas of the world. Highest incidence rates are seen in American Indians, people of Chile and other Latin American countries, Poland and North India. Though the incidence of carcinoma gallbladder in our country is no less than the western world, there is no broad-based study regarding this. So the exact incidence of carcinoma gallbladder in our country is not evaluated till now. But it is highly important to carry out a proper large scale study of these cancers in our country. Because the knowledge about the incidence, clinical presentations, evaluation of different patterns of treatment and natural history of the disease will invariably strengthen our efforts to combat the killer disease. Though it is not an uncommon disease in our country, there is dearth of information regarding this disease in this region. Pattern of presentation may also vary from other studies. By doing this, at least, awareness may be developed among the general people as well as the clinicians. For all these reasons, this has been chosen the topic of my study.

ANATOMY OF THE GALL BLADDER

Embryology of the gall bladder and biliary tree

The liver primordium appears in the middle of the third week as an outgrowth of the endodermal epitheliurn at the distal end of the foregut. This outgrowth, the hepatic diverticulum, or liver bud, consists of rapidly proliferating cells that penetrate the septum transversum, that is, the mesodermal plate between the pericardial cavity and the stalk of the yolk sac. While hepatic cells continue to penetrate the septum, the connection between the hepatic diverticulum and the foregut narrows, forming the bile duct. A small ventral outgrowth is formed by the bile duct and this outgrowth gives rise to the gall bladder and the cystic duct. Liver cords differentiate into the parenchyma and form the lining of the biliary ducts.3Gross anatomy of the gall bladder and biliary ducts

The hepatic ductal apparatus consists of intrahepatic and cxtrahepatic bile ducts. The extrahepatic ducts consist of

1 . The common hepatic duct, formed by the junction of the right and

left hepatic ducts.

2. The gall bladder, a reservoir of bile.

3. The cystic duct of the gall bladder.

4. The bile duct, formed by the junction of the common hepatic and cystic ducts 4,5,6.

Fig 1.1 Anatomy of gallbladder and bile ducts (Courtesy: http://catalog.nucleusi nc.com)

The common hepatic duct

The main right and left hepatic duct issued from the liver and unites near the right end of the porta hepatis as the common hepatic duct, which descends about 3 cm before being joined on its right at an acute angle by the cystic duct to form the main bile duct. The common hepatic duct lies to the right of the hepatic artery and anterior to portal vein5.

The gall bladder

The gall bladder is a slate blue, piriform sac partly sunk in a fossa in the right hepatic lobes inferior surface. It extends forwards from a point near the right end of the porta hepatis to the inferior hepatic border. It is 7-10 cm long, 3 cm broad at its widest and 30-50 ml in capacity. It is described as having a fundus, body and neck. The fundus, the expanded end, projects down, forwards and to the right, extending beyond the inferior border to contact the anterior abdominal wall behind the 9th costal cartilage. The body is directed up, back and to the left; near the right end of the porta it is continuous with the gall bladder neck. The neck (cervix) is narrow, curving up and forwards and then abruptly back and downwards, to become the cystic duct, at which transition there is a constriction. The neck is attached to the liver by loose connective tissue containing the cystic artery. The neck also shows a dilatation; the infundibulum (Hartmanns pouch), which hangs downwards and is often connected to the duodenum by folds, which may be either congenital or inflammatory in origin56The cystic duct

This structure is 3-4 cm long; it passes back, down and to the left from the neck of the gall bladder, joining the common hepatic duct to form the bile duct. Its mucosa forms spiral valve5.

The bile duct

The bile duct is formed near the porta hepatis, by the junction of the

cystic duct and common hepatic duct; it is usually about 7.5 cm long and

6 mm in diameter.

It is divided into four parts:

The supraduodenal portion, about 2.5 cm long, running in the free edge of lesser omentum.

The retroduodenal portion.

The infraduodenal portion lies in a groove but at times in a tunnel, on the posterior surface of the pancreas.

The intraduodenal portion passes obliquely through the wall of the second part of the duodenum where it is surrounded by the sphincter of Oddi. It terminates by opening on the summit of the ampulla of Vater.

Left of the descending part of the duodenum the bile duct reaches the pancreatic duct; together they enter the duodenal wall where they usually unite to form the hepatopancreatic ampulla, which opens on the summit of the major duodenal papilla

MICROSCOPIC STRUCTURE OF THE GALL BLADDER AND BILIARY DUCTS

1. The wall of the gall bladder displays three layers. The layers are: Serous, fibromuscular and mucous.

a. The serosa completely covers the fundus but only coats the inferior surfaces and sides of the body and neck of the gall bladder.

b. The fibromuscular layer is composed of fibrous tissue mixed with smooth muscle cells arranged loosely in longitudinal. circular and oblique bundle.

c. The mucosa is loosely connected with the fibrous layer, is generally yellowish brown and elevated into minute rugae with a honeycomb appearance.Its epithelium is a single layer of columnar cells. The mucous membrane contains indentations of the mucosa that sink into the muscle coat; these are the crypts of Luschka. There is no gland in the mucosa but mucus is secreted by the epithelium itself. The basal intercellular spaces show considerable dilatation and many capillaries lie close to the basement membrane. These features indicate active absorption of water and solutes from the bile, rendering it more concentrated. Mucous granules are present in the apical half of some cells, particularly those near the duct; these are secreted into the lumen.

2. The coats of the large biliary ducts arc an external of fibrous layer. The fibrous layer is composed of fibroareolar tissue; intermingled with a few non-striated muscle fibre that are arranged in a longitudinal, oblique and circular manner. The mucous layer is continuous with the lining membrane of the hepatic ducts and gall bladder and also with that of the duodenum. Its epithelium is of columnar variety.

Many lobulated mucous glands are present. In the bile ducts, the mucous membrane is provided with numerous tubulo-alveolar glands that secrete mucin.The circular muscle around the lower part of the bile duct, including the ampulla and the terminal part of the main pancreatic duct, is thickened and is called the sphincter of the hepatopancreatic ampulla (or the sphincter of Oddi). The later comprises musculature at three levels:

(i) at the end of the bile duct (sphincter ductus choledochus);

(ii) around the terminal part of the pancreatic duct (sphincter ductus pancreatici); and

(iii) around the ampulla.

Only the choledochal sphincter is constantly present 5.

Blood supply

Arterial supply

The cystic artery, usually from the right branch of the hepatic artery proper, it passes behind the common hepatic and over the cystic duct to the superior aspect of the gall bladders neck, on which it descends to divide in to superficial and deep branches. The former ramifies on the inferior, the latter on the superior aspect. An accessory cystic artery may arise from the common hepatic or one of its branches. The cystic artery supplies the hepatic ducts and upper part of the common bile duct. The lower part of the bile duct receives rami from the cystic artery. The right hepatic artery supply intermediate part through very small rami, the main supply being from the cystic and posterior superior pancreaticoduodenal arteries5.

Venous drainage

The cystic veins, which drain the gall bladder, vary. Those from its superior surface are in areolar tissue between the gall bladder and liver, usually entering the liver through the visceral fossa to join the hepatic veins. The remainder form one or two cystic veins which commonly also enter the liver either directly or after joining the veins draining the hepatic ducts and upper bile duct. Only rarely does a